Automatic vacuum packaging method



y 9, 6 J. R. HARDER 3,391,516

AUTOMATIC VACUUM PACKAGING METHOD Original Filed Feb. 1, 1965 2 Sheets-Sheet 1 LINE OF MOVEMENT July 9, 1968 J. R. HARDER AUTOMATIC VACUUM PACKAGING METHOD 2 Sheets-Sheet 2 Original Filed Feb.

3w Q g W N\\ I F I w s U H -al I. 8 h PW! NT w 8v WHHHH HQN e lw Unite States atent 3,391,516 AUTOMATIC VACUUM PACKAGHIG METHOD John R. Harder, Cedar Grove, NJ assignor to Mahaffy & Harder Engineering Company, Totowa, NJ. Continuation of application Ser. No. 429,457, Feb. 1, 1965. This application Aug. 4, 1967, Ser. No. 658,574 2 Claims. (Cl. 53-22) ABSTRACT OF THE DISCLOSURE Packaging apparatus for forming hermetically sealed and evacuated containers each consisting of a cup memher with a top sealed thereto, the apparatus having a number of trays movable together around an endless loop to carry cup members past operating stations where the top is sealed in place and the package is evacuated, there This application is a continuation of application Ser. No. 429,457, Feb. 1, 1965.

This invention relates to automatic packaging apparatus. More particularly, this invention relates to such apparatus for making evacuated packages. In the disclosed embodiment, one side of the package comprises a relatively stifl or semirigid board member, but the invention is useful with other types of packages such as those made entirely of flexible plastic film.

As shown in US. Patents 3,061,984 and 3,125,839, packaging apparatus has been provided comprising an endless train or receptacles travelling past a series of packaging stations arranged to produce in the receptacles packages made from two continuous sheets of flexible plastic film. One of these sheets is vacuum-formed down into the cavities of the receptacles to make cup-shaped package sections into which the products are loaded. The other sheet then is placed as a top across the open mouth of the formed package section and is heat-sealed thereto around the marginal edges of the receptacles so as to make air-tight containers. Copending application Ser. No. 213,705, filed by Mahaffy et al. on July 31, 1962, and copending application Ser. No. 368,926, filed by Mahaffy et al. on May 20, 1964, show still further developments in packaging apparatus of that general class.

Apparatus as disclosed in the above patents, and applications includes both a preliminary seal station and a final seal station. In the first of these stations, the two facing plastic sheets of the package are partially sealed together around their outer peripheries While leaving an unsealed area at an evacuation opening previously made by slitting the vacuum-formed package section. At the final seal station the package first is evacuated through the slit, and then the two sheets are sealed together around that opening to complete the package. These operations are carried out by a single packaging head which extends over both stations and moves vertically into and out of operation position.

At the final seal station, the packaging head includes a chamber positioned above the top of the container, and means are provided to evacuate that chamber to tend to keep the pressures on both sides of the top equal. However, there has been a problem with this approach resulting from the fact that the chamber pressure sometimes may decrease more rapidly than the interior pressure of the container. When that occurred with prior constructions, the top was apt to be blown up with suflicient force to tear the previously-formed preliminary seals, or to damage the top.

This problem has been solved in accordance with the present invention by evacuating the chamber through a vacuum port which is centrally located in the chamber and in position to be engaged by the container top if the latter is forced up too far by internal container pressure. When the top engages the vacuum port, it produces a self-valving action serving to reduce the rate of chamber evacuation and thereby restoring the pressure equilibrium. Thus damage to the package is avoided.

Accordingly, it is an object of this invention to provide improved vacuum packaging apparatus. A more specific object is to provide improved means and methods for evacuating packages. Other objects, aspects and advantages of the invention will in part be pointed out in, and in part apparent from, the following description considered together with the accompanying drawings, in which:

FIGURE 1 is a perspective view of a portion of a packaging machine embodying the present invention;

FIGURE 2 is a section taken along line 2-2 of FIG- URE 1, showing both the preliminary and final seal stations;

FIGURE 3 is a section taken along line 3-3 of FIG- URE 2; and

FIGURE 4 is a detail of the film clamp.

The apparatus shown in FIGURE 1 is a portion of a complete vacuum packaging machine of the general type shown in the above copending application Ser. No. 368,- 926. This machine comprises a large number of packaging dies in the form of trays 10, only two of which are shown. These trays are connected together in an endless loop and are driven with an intermittent indexing motion past a series of packaging stations. Each tray contains the usual two side-by-side package-forming cavities.

At one of the packaging stations preceding those shown in FIGURE 1, a thin film of plastic packaging material 12 is vacuum-formed down into the cavities of the trays 10 to form cup-shaped package sections which are loaded with the products to be packaged. Thereafter, a semirigid backing board 14 is placed on top of each tray, over the open mouth of the package section, and the tray is advanced to the preliminary seal station generally indicated in FIGURE 1 at 16.

Extending over this preliminary seal station 16 and the adjacent final seal station 18 is a packaging head 20. This head is shown in its tilted-back position simply to provide a better view of its construction. During normal operation of the machine, head 20 will be in a horizontal position, as shown in FIGURES 2 and 3, and is arranged to move vertically a small distance in synchronism with the motion of the rays 10, to provide clearance for the advance of the trays between each cycle of operations.

The preliminary seal section of head 20 comprises an electrically heated bar element generally indicated at 22. The peripheral portion 24 of this element is aligned with the outer edges of the trays 10 and, as in prior machines, is planar so that it can seat down against the flat board 14 to establish a marginal seal of the board to the plastic film 12. Heating element 22 additionally includes an arched portion 26 (see also FIGURE 2) bridged between the opposite planar portions 24 and overlying the tray partition 10a (FIGURE 3) dividing the two side-by-side tray cavities.

When the tray 19 reaches the preliminary seal station 16, and the head 20 has been moved down into operating position, air under pressure (3 psi.) is admitted into the interior of the package. The air is applied through the evacuation opening 28 and the tray chamber 30 containing the web-lifter 32, the latter being provided as dis- 3 closed in the above US patents to aid in the evacuation of the package when the tray reaches the final seal station.

The compressed air in the package presses the board 14 up against the gradually-relieved arched heater element 26 which in turn applies substantial heat to the contacted section of the board while the peripheral heater element 24 seals the outer edges of the board to the corresponding regions of the film. During this operation, the film remains secured in position on the tray, and thus the heat transferred to the board by arched heater element 26 does not effect any sealing of the film and board in that region. Plates 34 are provided to limit the upward movement of the board resulting from the compressed After the preliminary seal is complete, the head 20 is shifted up a small distance and the tray containing the partially sealed package is advanced to the final seal station 18. There the head 24 again comes down, and the web-lifter 32 is shifted up (by known means not shown) so as to arch the board 14 above the evacuation opening 28 and make possible a relatively rapid evacuation of the package. After evacuation (about 0.9 second), the weblifter drops down and the final seal bar 36 (FIGURE 1) is pressed down onto the board in the region around the evacuation opening. This heat and pressure, added to the heat already stored in the board by the heater element 26, is sufiicient to complete the seal within the very short time (about 0.1 second) remaining in the machine cycle. Thus two fully sealed, side-by-side packages are formed in the two tray cavities, and the machine thereafter advances the tray to conduct other necessary operations, i.e. to remove the packages, fold under the ends of the board 14 along the outboard score notches, and separate the packages along the center score notches.

While the package is being evacuated in the final seal station, the packaging head chamber 3 8 (FIGURE 2) above the board 14 is evacuated. This is for the purpose of equalizing the pressures on opposite sides of the board. It is difiicult as a practical matter to keep the chamber pressure exactly equal to the internal container pressure, and at times the chamber pressure will decrease more rapidly than desired. When this occurs, there is some danger that the board would be forced up, tending to tear the previously-formed preliminary seals, or tending to press the board against the chamber roof with suflicient force to damage it. To avoid these results, in accordance with the present invention, vacuum is introduced into chamber 38 through a port 40 which is centrally located in a position where the board can engage and cover the open mouth of the port if the board is pressed up too far. In that event, the board closes the port and, with a self-valving action, reduces the rate of evacuation of the chamber so as to restore pressure equilibrium with respect to the interior of the package.

As shown in FIGURE 3, each tray 10 is provided with recessed clamps 42 which hold the formed plastic film 12 in place. These clamps are arranged so that they open with a swinging movement, pivoting about the outboard end 42a when moved up by the spring-loaded actuator 44 at the preceding film-clamping station, illustrated at FIGURE 4. C-shaped member 46 at that station holds down the end 4211, and also serves to guide the film 12 in under the raised clamp.

The planar heater elements 24 include rearwardly extending cars 48 which overlap the packaging station immediately preceding the preliminary seal station 16. These ears serve to tack-seal the board 14 to the plastic film 12 in that preceding station for the purpose of maintaining the board in registery with the rest of the pack- 4 age while the tray is being advanced into the preliminary seal station.

Although a specific preferred embodiment of the invention has been set forth in detail, it is desired to emphasize that this is not intended to be exhaustive or necessarily limitative; on the contrary, the showing herein is for the purpose of illustrating the invention and thus enable others skilled in the art to adapt the invention in such ways as meet the requirements of particular applications, it being understood that various modifications may be made without departing from the scope of the invention as limited by the prior art.

I claim:

1. The method of making an evacuated package which comprises the steps of:

holding a cup-shaped package section in a correspond ing receptacle; placing a top of packaging material over the mouth of said package section to form a container therewith;

engaging said receptacle with a packaging head to seal said package section and said top from outside atmosphere;

evacuating said container;

withdrawing air from said packaging head through a vacuum port in the roof thereof during evacuation of said container, so as to tend to equalize the pressures on the inside and outside of said top;

closing off said vacuum port with an upwardly deformed portion of said top whenever the top tends to be excessively deformed up towards said packaging head roof by pressure differences between the inside and outside of said top; and

as part of the sequence of steps, sealing the top to the package section. 2. The method of making an evacuated package which comprises the steps of:

placing part of a first sheet of flexible packaging material in the cavity of a die having a marginal surface adjacent the periphery of the cavity 011 at least one side thereof, another part of said first sheet extending out over said marginal surface in the form of a flange with an opening therein;

applying a second sheet of packaging material to said die to cover said cavity and to form a container with said first sheet therein, one portion of said second sheet overlying said marginal surface of said die and covering said flange opening;

sealing said container from outside atmosphere by engaging said die with a packaging head forming a chamber over said second sheet;

pushing said sheet portion away from said flange to form an evacuation channel of substantial size into the interior of said container;

evacuating said container through said opening and said channel; evacuating said chamber through a vacuum port therein during evacuation of said container; and

restricting the flow of air through said vacuum port with said second sheet portion Whenever said portion is deformed by differential pressure sufficiently to reach said vacuum port; and

as part of the sequence of steps, sealing the second sheet to the first sheet.

References Cited UNITED STATES PATENTS 3,061,984 11/1962 Mahafiy 53-112X TRAVIS S. MCGEHEE, Primary Examiner. 

